I’ve transferred funds into my Trezor on MM but I’m unable to transfer/send funds out.
When prompted I’m asked for my passphrase but I’m pretty sure I didn’t set one up, I think I only set up a standard wallet.
Even when I proceed without entering a passphrase it still comes up as transaction failed.
It looks as if I’ve forget my passphrase but I’m pretty sure I didn’t set one up.
Metamask is most probably preventing you from spending your funds because you are not using appropriate private key (you are not using correct combination of seed and passphrase).
Are you able to find the address that you are trying to spend from using following tool: https://findeth.io/